Who is the “expert” to whom Swift refers in "A Modest Proposal"?

Throughout this excellent satirical essay, Jonathan Swift
appeals to the expert advice of a number of individuals to support his argument and give
what he is saying an illusion of credibility. It is important to realise that Swift
deliberately uses this to heighten the element of satire in this clearly ludicrous
proposal: throughout the essay he strikes a reasonable, carefully calculating tone, to
which the appeal to experts adds weight. Note how he does this in the following
example:

I
have been assured by a very knowing American of my acquaintance in London, that a young
healthy child well nursed is at a year old a most delicious, nourishing, and wholesome
food, whether stewed, roasted, baked, or boiled, and I make no doubt that it will
equally serve in a fricassee, or
ragout.

Here, the overt
appeal for credibility, achieved through reference to a "very knowing American" is
completely undercut through the understanding that the label "American" in the time of
Swift would automatically be associated with a barbaric person. So, whilst the "expert"
he refers to goes unnamed, it is important to identify how Swift's appeal to expert
advice is used by him to heighten the element of satire in this provocative
and challenging essay.